Furnace roof construction



Jame 4, 1946. w. H. PAYNE FURNACE ROOF CONSTRUCTION Filed Sept. 16, 1945,2 AWN Patented June 4, 1946 UNITED STATES PATENT OFFICE FURNACE ROOFCONSTRUCTION William Harvey Payne, La Grange, Ill.

Application September 16, 1943, Serial No. 502,651

9 Claims.

The present invention relates to improvements in electric arc meltingfurnaces with particular respect to the top charge type of electricmelting arc furnaces.

Present top charge designs use lift-rollout roof mechanisms or roof liftswing-a-side designs. Some have separatel located roof swing-a-sideunits from the shell proper and others have the roof lift swing-a-sidemechanisms fastened directly to the electric furnace shells.

One of the troubles with these types of equipment in the past has beenthat in operation the entire weight load of the roof and itsrefractories and electrodes and arms and back. plate mechanism, verticalextensions, and, in fact, all mechanism that goes with the top chargeswing-a-side group is thrown on the side wall refractories of theelectric furnace to be supported thereby inbetween times when thefurnace is not being charged. As an example, in the case of a 6-tonfurnace with an 11 ft. diameter shell, this swinga-side mechanism weighsabout 18,000 lbs. total. Practically 95% of the time an electric furnaceis in operation. this entire Weight is normally supported on the sidewall refractories of the furnace shell. While these side wallrefractories are thick and new, they will support this load fairly well,but toward the end of a refractory run, when the side walls get down to3 inches or more in thickness, this tremendous mechanical load is aburden to such an extent that the refractories will be crushed and shortrefractory life is the result.

The present invention which is concerned with the problem of reducingthis dead load weight on the side wall refractories to any desiredpercentage may be exemplified by the hydraulic mechanism disclosed inthe accompanying drawing.

In the drawing l represents a furnace having a swing cover ll carried byan arm l2, the outer end of which is rigidly secured to a verticallymovable cylinder l3 enclosing the upper end of a fixed piston post l4suitably supported and secured to the furnace wall by a brace l5. Theconstruction is one which permits pressure to be admitted under theupper closed end of the movable cylinder to react against the pistonpost in lifting the arm which supports the cover so that the cover maybe swung laterally upon the post as a pivot to open the top of thefurnace for charging. After the charge is dropped into the furnace, theroof is again swung back over the furnace crucible, and lowered intoplace, being supported on the side wall refractories.

The above features are of standard construction and, the presentinvention now to be described is directed to the means provided foreasing the pressure of the cover upon the side walls by maintaining anupwardly directed pressure under the cylinder head which will in partcounterbalance the weight of the cover.

In lifting the cover, a liquid, preferably oil, under pressure isadmitted to the cylinder through flexible pipe l6 controlled by two-wayvalve I! having passages l8 and l9 which when turned as shown in fulllines will establish communication through passage ill with pressureline 20 which includes a pump 2| driven by a motor 22 which, forexample, may have a capacity to maintain a pressure of 400 lbs. p. s. i.

The valve ll when turned to the position indicated in dotted linesestablishes communication between flexible pipe l6 and return lin 23including relief valve 24 set to maintain a pressure of, for example,100 lbs. p. s. i. The return line leads to the base of an oil storagetank 25 from which oil is supplied to the pump through pipe 26.

The supply pipe l6 connects with return line 28 through cross pipe 2'!including relief valve 28 which may be set to open at a pressureslightly in excess of the pump pressure as, for instance, 450 lbs. p. s.i. A reducing valve 29 in connection 30 between the supply and returnlines is provided for a purpose to be presently explained. I

With the two-way valve turned to the dotted line position, communicationwill be established between the upper leg of the supply pipe and thereturn line, and in these circumstances a pressure of say 100 lbs. p. s.i. will be maintained beneath the head of the movable cylinder, so thatthe lowering of the furnace cover will be cushioned and its weightpartially counter-balanced and the none-toostrong refractory furnacewalls relieved in part from the pressure of the cover. This min.- imumpressure will be maintained and renewed in the return line by thepressure admitted through the reducing valve 29 which is a standardpiece of equipment which is in connection with the superior pressureconstantly maintained in the supply pipe l6 by the action of the pump orby air under pressure acting against the oil supply or by any otherequivalent agency.

Others have attempted to attain a similar result by the use ofadjustable screws and wedges on the top of the furnace shell which,however, require frequent adjustment and attention on the part of theoperator as the roof refractories expand and contract in order to takethe load off the refractories. Such expedients are unsatisinconstruction and certain in operation and is of a nature which readilypermits adjustments. in the degree of pressure to be employed forlifting and counter-balancing purposes to best meet the ends in view.

I claim:

1. In mechanism of the class described, the

combination of a furnace, a roof adapted to rest upon the furnace walls,and mountings therefor adapted to permit the roof to be lifted to openthe topof the furnace, said mountings including a vertically movablecylinder closed at its'upper end, and a fixed piston post enteredthereinto and adapted to aiford'resistance to a medium under pressureadmitted between'the piston post and the closed upper end of thecylinder, means for I enclosing a columnof liquid and communicating withthe space between the cylinder and thepiston post, a liquid columnenclosed within said means, an agency for applying to said liquid columna degree of pressure in excess of the weight of the cover and partsmovable therewith to lift the cover from the furnace, and meanseffective to relieve the pressure to lower the cover and thereafterautomatically maintain "a constant substantially uniformreduced'pressure on said column adapted to act as a, partialcounter-balance for reducing the weight of the load supported by thewalls of the furnace.

2. In mechanism of the class described, the

4 between the cylinder and the piston, a liquid column enclosed withinsaid means, an agency for applying to said liquid column a degree ofpressure in excess of the weight of the cover and parts movabletherewith to lift the cover from the furnace, and means effective torelieve the pressure to lower the cover and thereafter automaticallymaintain a. constant substantially uniform reduced pressureon saidcolumn adapted to act as a partial counter-balance for reducing theweight of the load supported by the walls of the furnace.

4; In mechanism of the class described, the

combination of a furnace, a roof adapted to rest upon the furnace walls,and mountings therefor adapted-to permit the roof to be lifted and swunglaterally to open the top of the furnace, said mountings including acylinder and piston movable vertically relatively to one another, themovable element being effective to lift the cover when a medium underadequate pressureis admitted between the cylinder and piston, means forenclosing a column of liquid and communicating with the space betweenthe cylinder and the piston, a liquid column enclosed within said means,an agency for applying to said liquid column a degree of pressure inexcess of the weight of the cover and parts movable therewith to liftthe cover from the furnace, and means effective to relieve the pressureto lower the cover and thereafter automatically maintain a constantsubstantially uniform reduced pressure on said column adapted to act asa partial counter-balance for reducing the weight of the load supportedby the walls of the furnace.

5. In mechanism of the class described, the combination of a furnace, aroof, and mountings therefor adapted to permit the roof to be lifted toopen the top of the furnace, said mountings combination of a furnace, aroof adapted to rest upon the furnace walls, and mountings thereforadapted to permit the roof to be lifted'and swun laterally to open thetop of the furnace; said mountings including a vertically movablecylinder closed at its upper end, and a fixed piston p'o'st enteredthereinto and adapted to afford resistance to a medium under pressureadmitted between the piston post and the'closed upper end of thecylinder, means for enclosing a-columnof liquid and communicating withthe space-between the cylinder and the piston p'ost,a liquid columnenclosed within said means, an agency for applying to said liquid columna degree of pressure in excess of the weight of the cover and partsmovable therewith to lift the cover from the furnace, and meanseffective to relieve the pressure thereafter automatically lower thecover and to maintain a constant substantially uniform reduced pressureon said column adapted to act as a p r tial counter-balance for reducingthe weight of the load supported by the walls ofthe furnace 3. Inmechanism 'of the class described, the combination of'a furnace; a roofadapted to; rest upon the furnace walls, and mountings-therefor adaptedto permit the roof to be lifted to 'open the top of the furnace, saidmountings including a cylinder and piston movable vertically relativelyto one another, the movable element being effective to lift the coverwhen a' medium under adequate pressure is admitted between the umn fliquid and communicating with the space including a cylinder and pistonmovable vertically relatively to one another, the movable element beingeffective to'lift the cover when a medium under adequate pressure isadmitted between the cylinder and piston, asupply pipe line forenclosing a column of liquid, said pipe line communicating with thespace between the cylinder and piston, a liquid column enclosed within'said pipe line, an agency for applying to said liquid column a degree ofpressurein excess of the weight of thecover and parts movable therewithto lift the cover from the furnace, a return line and valve means forestablishing communication between the cylinder and either the supply orthe return line, a relief valve in the return line adapted to open undera degree of pressure less than that required to lift the cover and toclose when pressure has been reduced to an intended degree to afford a:partial counter-balancing pressure between the cylinder and piston. r P1 f Y 6. In mechanism of the class described, the combination of afurnace, a roof, andmountings therefor adapted to permit the roof to belifted and swung laterally to open the-top of the furnace, saidmountings-including a cylinder and piston movable vertically relativelyto one an-, other, the -movable element being effective to lift thecover when a medium-under adequate pressure is admitted between thecylinder and piston,'a supply pipe line for-enclosing a column ofliquid, said pipe line communicating with the space between the cylinderand piston, a liquid column enclosed within said pipe line, an agencyfor applying to said liquid column a degree: of pressure in excess ofthe weight of the cover and parts movable therewith to lift the coverfrom the furnace, a return line and valve means for establishingcommunication between the cylinder and either the supply or the returnline, a relief valve in the return line adapted to open under a degreeof pressure less than that required to lift the cover and to close whenpressure has been reduced to an intended degree to afford a partialcounter-balancing pressure between the cylinder and piston, and areducing valve between the supply and return lines adapted to maintainthe intended partial counter-balancing pressure.

'7. In a mechanism of the class described, the combination of a furnace,a roof adapted to rest upon the furnace walls, and mountings thereforadapted to permit the roof to be lifted to open the top of the furnace,said mountings including a vertically disposed cylinder and a pistonentered thereinto and forming an expansion chamber therewith, a sourceof higher pressure and a source of lower pressure and means forconnecting the expansion chamber alternatively to the source of higherpressure and to the source of lower pressure; said higher pressure beingsufficient to overcome the weight of the cover and parts movabletherewith to lift the cover from the furnace, and said lower pressurebeing substantially uniform and acting as a partial counter-balance forreducing the weight of the load supported by the Walls of the furnace.

8. In a mechanism of the class described, the

combination of a furnace, a roof adapted to rest upon the furnace walls,and mountings therefor adapted to relieve the walls of a substantialpart of the load of the roof, said mountings including a cylinder and apiston entered therein to form an expansion chamber therewith, and meansfor supplying to the expansion chamber fluid under a pressureautomatically maintained sufficient to relieve the walls of asubstantial part of the load of the roof but insufficient to raise theroof therefrom.

9. In a mechanism of the class described, the combination of a furnace,a roof adapted to rest upon the furnace walls, and mountings thereforadapted to permit the roof to be lifted to open the top of the furnace,said mountings including a vertically disposed cylinder and a pistonentered thereinto and forming an expansion chamber therewith, a sourceof higher pressure and a means for pressure relief to lower the pressureand means for connecting the expansion chamber alternatively to thesource of higher pressure and to that of lower pressure; said higherpressure being sufficient to overcome the weight of the cover and partsmovable therewith to lift the cover from the furnace, and means tomaintain said lower pressure substantially uniform and acting as apartial counter-balance for reducing the weight of the load supported bythe walls of the furnace.

WILLIAM HARVEY PAYNE.

